Re: Slow receive with rtl8192cu (usb ew-7811Un)

[Larry Finger <Larry.Finger@lwfinger.net>]

On 05/16/2011 10:57 PM, Rob Browning wrote:
> Rob Browning<rlb@defaultvalue.org>  writes:
>
>> So that command ran at essentially the rates you report for 10-20
>> seconds.  Then I killed it and tried another test I'd been using, which
>> was to lftp to ftp.kernel.org and get -c linux-2.6.39-rc7.tar.bz2.  That
>> transfer started at a high rate, but settled fairly quickly at about
>> 60KB/s.  So I killed that transfer and restarted the wget, and it ran
>> steadily at ~60KB/s.
>
> In case it helps, it also looks like the 60KB/s is an aggregate limit.
> Once it gets into the "lower bandwidth" state, if I run multiple
> transfers, the total won't go above that.

I can duplicate your result. To me, it appears to be a problem with bufferbloat. 
If that is correct, then there is little I can do with rtl8192cu to fix the 
problem. I see exactly the same slow rate with rt2800usb using an Ralink RT3070 
device. In addition, I see that rate when connected to my router with a wired 
100 Mbps connection.

What up/down rates do you see if you test with www.speedtest.net? I get 0.48 
Mbps up and 12.03 Mbps down. The up rate is a little slower than the 512 Kbps 
that my ISP provides. My nominal down rate is 7 Mbps with burst rates above 10 
if the bandwidth is available. Apparently it was this morning.

Larry